Saturday, 3 January 2009

The Sargasso Sea

Each year, about 1,700 million tonnes of dust are produced by deserts around the world and obout one third of this falls into the oceans. In fact, a staggering 40 million tonnes of dust is transported from the Sahara to the Amazon each year. The sand and dust are rich in nutrients and minerals. The dust blown across the Atlantic falls into the sea, where the minerals are thought to fertilize the ocean. Deep within the Atlantic Ocean, near the Bermuda Triangle, lies a sea shrouded with mystery - named the Sargasso Sea. The sea is named after a seaweed which is unique to the area - sargassum.

The Sargasso's currents are largely immobile yet surrounded by some of the strongest currents in the world. Although most scientists thought that this expanse of sea contained no sustainable life, observations showed that oxygen and other elements were being consumed at a higher rate than theories and models could account for. This led scientists to think there must be some nutrient source fueling the blooms of phytoplankton in the Sargasso Sea ( Carlowicz, 2006; LiveScience). This discovery, in turn, led to the discovery of eddies.

Eddies are the internal weather of the sea - the oceanic equivalent of storms in the atmosphere. The largest eddies can contain upto 1,200 cubic miles of water and can last from months to a year. Eddy-driven nutrient transport actually primes the ocean's 'biological pump' fertilizing the waters with nutrients from the deep. Fed by this unusual upwelling, the phytoplankton population greatly increases, and in-turn, attracts more zooplankton and other animals higher up the food chain. The fate of all that biomass also is important as plankton blooms can remove substantial amounts of carbon dioxide from surface waters, and sink it to the deep ocean.

I am reminded of so many things here. I think of mountains that are so large that they generate their own weather. It would also appear that the Sargasso Sea creates its own weather. The Sargasso Sea is found above the seafloor that is the Nares Abyssal Plain which has a maximum depth of 6,491 meters. As some kind of comparison, Mount Kilimanjaro stands at 5,885 meters above sea-level. ( I'm unsure of its relevance, but I'm also reminded of how forest wildfires produce their own weather)

Then there is the obvious comparison of eddy-currents in the Sargasso Sea, and those eddy-currents which are an electrical phenomena as discovered by French physicist Leon Foucalt in 1851. A magnet moved near a solid mass, or plate of metal, induces in it currents which, in flowing through it from one point to another, have their energy frittered down into heat, and which, while they last, produce (in accordance with Lenz's law) electromagnetic forces tending to stop the motion. An eddy-current is the current induced in little swirls ('eddies'). If the waters of the Sargasso Sea act as eddies - what is creating the imposed magnetic field?

Water is a conductor. Salty water is an excellent conductor. The water of the Sargasso Sea is said to be salty, and warm, maintaining a salinity around 36%, and euphotic zone temperature up to 22 c. The northern region contains warm water known as eighteen-degree water that moves outwards along the surface of the sea, allowing it to maintain that temperature year round whereas coastal waters with the same latitudes freeze in the winter. So perhaps here we have a little evidence of the heat generated by electrical eddy-currents.

Work is done when lifting a grain of sand off the ground to a certain height, because the sand's potential energy changes. I'm trying to imagine what happens as 1,700 million tonnes of the stuff is transformed from potential energy into kinetic energy. We have seen the spectacular effects from the electrolysis of minerals on-board comets - so what could be the effects of mineral rich dust? What effects (if any) does this have on the atmospheric weather systems, and the systems of the sea?

The Sargasso is an oasis of calm surrounded by strong currents; my mind is drawn to hurricanes. The eye of a hurricane is well known for its calm winds, and being surrounded by a ring of towering thunderstorms where the most severe weather of a cyclone occurs.(As a point of interest, hurricanes develop in the southern part of the North Atlantic Ocean).

There are five major ocean-wide gyres - the North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Ocean Gyres. These are giant circular surface currents that sweep around the major ocean basins. Mid-ocean gyres are known as 'ocean deserts'. Is a pattern starting to appear in connection with the 'skin-effect' of electrical flow in conductors? Where electricity does not simply flow in the core of the conductor, but flows outside on the skin.

Many thanks:

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